Conventionally, there is a method for projecting one image such that some or all of the projection images projected from a plurality of projectors mutually overlap. In such a part where projection images overlap (which will be denoted as overlap region), its luminance can be different from that in other region or the overlapping projection images can be offset.
Therefore, there has been assumed that such an overlap region is sensed by a camera to detect how the overlap is and an image to be projected is corrected depending on the detection result. In this case, it is necessary to grasp the correspondences of pixels between a projector for projecting an image and a camera for shooting its projection image.
A method using gray code has been considered as a method for acquiring the correspondences of pixels. With the method, however, many pattern images need to be used for discriminating each pixel of the projector, and thus the processing of grasping the correspondences of pixels can be complicated.
Thus, there has been proposed a method for projecting a checker and four patterns in which any of the four corners of the checker is missing and matching the order of projection of the patterns with the information on the missing corners thereby to detect a correspondence between each corner of the checker and a pixel of the projector (see Non-Patent Document 1, for example).